1. Field of the Invention
This invention relates to a fluid-impermeable composite hose. More particularly, it relates to a fluid-impermeable hose having a composite wall including a fluid-impermeable laminated layer formed of a laminated sheet which contains a metallic foil, or a metallic layer formed by vapor deposition. The hose of this invention is particularly useful as a fluid-impermeable hose for transporting any of various kinds of fluids in a motor vehicle.
2. Description of the Related Art
It is strongly desired in view of system maintenance, environmental protection, etc. that every hose used for transporting a refrigerant, such as carbon dioxide, in an air-conditioning system on a motor vehicle be impermeable to the refrigerant. One of the most effective approaches lies in a hose having a laminated wall layer which contains a metallic foil, or a metallic layer formed by vapor deposition. Environmental protection also requires a fuel hose to be impermeable to fuel, and a laminated wall layer is very useful for a fuel hose, too.
It has hitherto been usual to form a laminated wall layer for a hose by the longitudinal lapping or spiral winding of a tape of a laminated sheet containing a metallic foil, or a metallic layer formed by vapor deposition. Longitudinal lapping is a method in which a tape of a laminated sheet having a width large enough to encircle a hose to be made is placed in parallel to the longitudinal axis of the hose and bent into a cylindrical layer. Spiral winding is a method in which a tape of a laminated sheet is wound spirally to form a cylindrical layer.
Spiral winding is preferred to ensure that a hose installed on a motor vehicle be flexible enough to withstand any vibration of the vehicle or its engine. A spirally wound laminated sheet usually has a pair of spirally extending edge portions overlapping each other to ensure the formation of a laminated layer of high fluid impermeability. Such a way of spiral winding, however, presents a serious problem as is illustrated in a somewhat exaggerated way in FIG. 1. While no problem may occur to a first turn 1a of a spirally wound sheet 1, a second turn 1b thereof wound in a partly overlapping way has a loose edge portion 3 raised above the first turn 1a by a rear edge 2 thereof. The looseness of the raised edge portion 3 is gradually accumulated with an increase of spiral turns until it eventually becomes folded to absorb its looseness. The folds formed on the laminated layer at certain intervals lower the fluid impermeability of the hose seriously.
A thin and stretchable tape can usually be wound spirally about a cylindrical body without having either edge thereof raised, since it is curved into an S-shaped form across its width, as shown at 4 in FIG. 2. The laminated sheet under discussion, however, necessarily has a somewhat larger thickness, insofar as it has a multilayer structure in which a metallic foil, or a metallic layer formed by vapor deposition is interposed between a pair of resin films. Its stretchability has to be low enough to avoid the fracture of e.g. the foil by stretching. Therefore, the laminated sheet is difficult to wind spirally as shown in FIG. 2, and can only be wound as shown in FIG. 1.
It is an object of this invention to provide a fluid-impermeable composite hose having a laminated layer formed by winding a tape of a laminated sheet spirally, which is satisfactorily high in flexibility and is free from the problem as pointed out above.
The inventors of this invention have conceived of forming a laminated layer by winding a tape of a laminated sheet spirally in a way leaving a gap between every two adjoining turns, and winding a further tape spirally over such a gap. The laminated layer has overlapping portions as required, while giving the hose the necessary flexibility. Moreover, it is not folded as shown in FIG. 2.
According to a first aspect of this invention, there is provided a fluid-impermeable composite hose having a wall comprising a fluid-impermeable laminated layer formed of a laminated sheet which contains a metallic foil, or a metallic layer formed by vapor deposition, wherein the laminated layer comprises an inner winding layer formed by winding a tape of the laminated sheet spirally in a single layer and leaving a gap between every two adjoining turns, and an outer winding layer formed by winding another tape of the laminated sheet spirally in a single layer over the gap in the inner winding layer and leaving a gap between every two adjoining turns.
The inner winding layer 6 is a single spirally wound layer having a gap 6a between every two adjoining turns, as shown in FIG. 3. Therefore, it does not have any loosely raised edge portion of the nature mentioned before in connection with the related art. It does not form any fold which may lower the fluid impermeability of the hose seriously. The outer winding layer 7 does not form any such fold, either, since it is also a single spirally wound layer having a gap between every two adjoining turns.
The gap 6a in the inner winding layer does not affect the fluid impermeability of the hose at all, since it is covered by the outer winding layer 7. The gap 6a improves the flexibility of the hose, since it provides a space allowing for the bending of a cylindrical base 8, which may, for example, be a rubber layer. Although the laminated layer is formed of two winding layers, the hose is comparable in flexibility to any known hose having a single spirally wound laminated layer, since the gap 6a remains as it is after the winding of the outer layer, as shown in FIG. 3.
According to a second aspect of this invention, the gap in the inner winding layer has the maximum possible width, and is covered by the outer winding layer overlapping the inner winding layer appropriately. The maximum possible width of the gap 6a ensures the still higher flexibility of the hose.
According to a third aspect of this invention, the gap in the inner winding layer has a width of at least 1 mm. Although the width of the gap may depend on the flexibility as required of the hose and the width of the laminated sheet employed for the inner and outer winding layers, it provides a preferable example of a width of the gap.
According to a fourth aspect of this invention, the laminated sheet comprises one of the following (1) to (3) and a resin film or films laminated thereon:
(1) a metallic foil;
(2) a metallic foil with a reinforcing material; and
(3) a metallic layer formed by vapor deposition.
The laminated sheet containing (1) or (3) has the advantage of being relatively small in thickness, while the sheet containing (2) has the advantage that its foil is reinforced against fracture.
According to a fifth aspect of this invention, the laminated sheet satisfies at least one of the following requirements (4) to (6):
(4) it has a thickness not exceeding 250 xcexcm;
(5) it contains a film or films of a polyamide (PA), polyethylene terephthalate (PET), or ethylene-vinyl alcohol (EVOH) resin; and
(6) the resin film or films are of a material having an flexural modulus of at least 300 MPa.
These requirements make it possible to ensure the flexibility of the hose. These resins are all high in flexibility and tensile strength. A resin having a high flexural modulus gives the laminated sheet flexibility without giving it stretchability.
According to a sixth aspect of this invention, the inner and outer winding layers are bonded to each other in their overlapping portions. The hose has a still higher level of fluid impermeability.
According to a seventh aspect of this invention, the wall of the hose comprises one of the following layer combinations (7) to (10), each sequentially from the radially innermost layer:
(7) an inner rubber layer/the laminated layer/an intermediate rubber layer/a reinforcing layer/an outer rubber layer;
(8) a thin resin layer/an intermediate rubber layer/the laminated layer/an intermediate rubber layer/a reinforcing layer/an outer rubber layer;
(9) a thin resin layer/the laminated layer/a thin resin layer/an intermediate rubber layer/a reinforcing layer/an outer rubber layer; and
(10) an inner rubber layer/a thin resin layer/the laminated layer/a thin resin layer/an intermediate rubber layer/a reinforcing layer/an outer rubber layer.
These are a few typical examples of layer combinations for the wall of the hose according to this invention.
The above and other features and advantages of this invention will become more apparent from the following description and the accompanying drawings.